Generating a high concentration ratio of solar radiation at a fixed focal point is useful for a variety of applications. A point concentrator can generate a higher concentration ratio of solar radiation than a linear concentrator. Two commercially known point concentrators are solar power tower systems and parabolic dish systems. Solar power tower systems rely on an array of dual-axis tracking reflectors (heliostats) that concentrate sunlight on a central receiver atop a tower. As a result of Incident Angle Modification (IAM), solar power towers have the disadvantage of low optical solar efficiency. Furthermore, the position of the receiver atop the tower makes it difficult to maintain. Alternatively, parabolic dish systems have a high optical solar efficiency due to an IAM that is up to 1.0. Commercially known parabolic dish systems have the disadvantage of a moving focal point and a high wind load that limits the size of the dish to around 10 meters in diameter. Furthermore, the elevated position of the receiver, between the dish and the sun, makes it difficult to reach and maintain.
There are existing concentrators (also referred to as lower focal point concentrators) that are configured to focus solar radiation to a focal point located thereunder, opposite the sun. Examples include refractive lenses, either smooth imaging lenses or Fresnel type transparent lenses. However, producing large glass or plastic lenses is often not practical and/or cost prohibitive. Furthermore, the wind load of such lenses limits their size to less than 10 meters in diameter. Any larger and the lens can be easily broken.
U.S. Pat. No. 6,620,995 (“'995 patent”) discloses another example lower focal point concentrator that is configured to focus solar radiation to a focal point located thereunder, the center of the focal point is fixed with respect to the ground. However, the '995 patent describes a concentrator where the reflector rings all have the same width resulting in an un-even concentration ratio of solar energy at the focal point. Further, the reflective surface of each reflector ring is concave. Still further, the '995 patent does not disclose a suitable tracking apparatus for use with the disclosed concentrator.
Once a nonmoving focal point (or area) for solar radiation has been formed by a concentrator, the heat generated at the focal point may have many applications. For example, the heat generated at the focal point may be used to heat an energy receiver configured to act as the melting pot of a metal smelter. The heat generated at the focal point may be used to heat up a hot air receiver operably connected to a Brayton cycle gas turbine which may be the first part of a combined cycle gas turbine system. At this time, combined cycle gas turbine systems have the highest thermal to electrical efficiency known to those of ordinary skill in the art. Furthermore, a thermolysis device, or a portion thereof, may be positioned at the focal point of the concentrator. In this way, the thermolysis device can split water into hydrogen and oxygen using the high temperatures generated at the focal point. The produced hydrogen may be reacted with atmospheric CO2 to produce a variety of liquid fuels.
The present invention discloses a system configured to track the sun and focus radiant energy (i.e., sunbeams) striking a non-imaging concentrator onto a receiver positioned thereunder. The system disclosed herein provides ring-like reflective elements, each ring-like reflective element includes a reflective surface having a unique width, that are configured to evenly concentrate the Sun's radiant energy across the entire diameter of the focal point (or area) of the concentrator. The non-imaging concentrator of the present disclosure can be made of a reflective metal, or another suitable reflective material, and is configured to allow wind to flow through the ring-like reflective elements thereof. As such, the non-imaging concentrator is not limited to a maximum diameter of ˜10 meters making it suitable for commercial applications (e.g., energy generation, metal smelting, thermolysis, etc.).